A steel pipe with excellent inner surface texture is conventionally produced by a blasting device capable of wiping or polishing the inner surface of the steel pipe to remove scale on the inner surface of the steel pipe or polish the inner surface of the steel pipe by feeding a wiping or a polishing material via a carrier fluid from one end of the steel pipe and blasting the inner surface of the steel pipe with that wiping or polishing material.
These types of blasting devices are typically known as high-pressure injection blasting devices and negative-pressure suction blasting devices.
The high-pressure injection blasting device removes scale on the inner surface of the steel pipe or polishes the inner surface of the steel pipe by feeding a wiping or polishing material via high-pressure air as a carrier fluid and injecting this material into the steel pipe from one end to blast the inner surface of the steel pipe with this wiping or polishing material. The wiping or polishing material fed into the steel pipe by high-pressure air is then recovered in a recovery tank with filter, installed at the other end of the steel pipe.
In the negative-pressure suction blasting device on the other hand, the wiping or polishing material stored in a supply unit mounted near the beginning portion of the steel pipe is injected into the steel pipe from one end of the steel pipe, and air is suctioned from the other end of the steel pipe via a blower. Here, inside of the steel pipe is regulated to be negative-pressure, the wiping or polishing material is fed by a negative-pressure airflow generated by the negative-pressure and blasting the inner surface of the steel pipe with the wiping or polishing material to remove scale on the inner surface of the steel pipe or to polish the inner surface of the steel pipe. Note that, this wiping or polishing material fed inside the steel pipe by negative-pressure airflow is suctioned by a blower at the other end of the steel pipe and discharged outside the pipe. The wiping or polishing material is however recovered by any of a gravity drop type dust collector, cyclone, or dust collector with a filter provided between the other end of the steel pipe and the blower, or recovered by a combination thereof, and a portion of the wiping or polishing material is recycled.
In regard to such high pressure injection blasting device and negative-pressure suction blasting device, there is Patent document 1 described below. Along with describing respective problems with conventional high-pressure injection blasting devices and negative-pressure suction blasting devices, this document discloses a blasting device that is an improvement on conventional negative-pressure suction blasting devices. In other words, in a negative-pressure suction blasting device, when a wiping material or polishing material is fed to the vicinity of the beginning portion of the steel pipe by a negative-pressure airflow suctioned into a steel pipe resulting from negative pressure inside a steel pipe, it is proposed that a shape of supply part for a wiping or polishing material provided in the vicinity of beginning portion of the steel pipe should be improved in order to swirl the negative-pressure airflow.
[Patent document 1] JP 5-228842A